| Hydrogen,as a new energy source,is widely used in the industrial production process.However,due to its high reactivity,hydrogen has a greater risk of combustion and explosion in the process of utilization,storage and production.When hydrogen production room,explosion,such as space between hydrogen storage room light walls,doors and Windows will be destroyed first and explosion venting structure formation,indoor hydrogen quickly by the vent discharge to the outdoor and combustible gas cloud formation,when the explosion flame propagation to outdoor could ignite combustible gas cloud and induce strong external explosion,lead to serious secondary disasters,pose a threat to neighboring districts.To systematically understand the mechanism and characteristics of hydrogen external explosion,the influence of various factors on the dynamic of outdoor transient flow field induced by premix hydrogen/air explosion and the law of disaster was studied by means of computational fluid dynamics.The main findings are as follows.(1)The influence of the opening pressure,opening time and scaled vent size on the dynamic mechanism and characteristics of external explosion was explored.The P_v and t_v had the same influence law on the external flow field,that is,the range of external gas cloud,turbulent kinetic energy(TKE)and combustion intensity of jet flame all decreased with the increased of both.The external explosion intensity increased significantly with the increased of P_v and t_v and the decreased of K_v.With the increased of P_v,t_v and K_v,the external explosion wave and film breaking shock wave showed obvious superposition phenomenon.The explosion wind speed could reach more than 8 times of the hurricane wind speed,so the significantly increased high-speed air flow caused by vent parameters is the main cause of the damage to the environment,and is also one of the main risk factors of explosion hazard.(2)The influence of ignition position on the dynamical mechanism and characteristics of external explosions was studied.As the ignition was far away from the vent,the further the range of the venting gas cloud was,the larger the peak TKE and turbulent area would be.No external explosion was observed when the front ignition.As the ignition was far away from the vent,the external explosion intensity increased.When the rear ignition,the superposition effect of the external explosion wave and the film breaking shock wave was induced significantly,thus expanding the damage range of outdoor venting overpressure.The farther the ignition was from the vent,the greater the damage area caused by outdoor overpressure,high temperature range and gas flow.(3)The influence of hydrogen concentration on the dynamical mechanism and characteristics of external explosions was investigated.With the increased of hydrogen concentration,the TKE,the turbulent area and the combustion intensity of vented flame all showed a trend of increasing first and then decreasing.Whenφ=40%,the external explosion intensity was the maximum,and the new shock overpressure even exceeded the maximum external explosion overpressure,which posed a serious threat to outdoor structures and personnel with a longer distance.In addition,with the increase of hydrogen concentration,the maximum outdoor peak temperature increased first and then decreased,while the maximum peak wind speed increased all the time.(4)The correlation law between external explosion and flow field parameters was clarified.The external explosion overpressure was positively correlated with the vented flame velocity and TKE under different vent parameters.The external explosion intensity was mainly related to the combustion intensity of external gas cloud,the location of external explosion was mainly determined by the range of unburned cloud,and the external explosion time was jointly determined by the vented flame velocity and the range of unburned cloud.Turbulence was considered as an indirect factor affecting the external explosion characteristics,which promotes the external explosion intensity,location and time. |
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